Информация для dc-netplay-4.0-163

Fix freeze on close - bFF_GPReadEnable was not enough to stop SyncGPU.
Should look into the potential performance impact of having GPUHasWork
test so many different things - RunGpuLoop already did this, and SyncGPU
doing it once-ish per frame probably doesn't matter, but it might be
possible to make cheaper anyway.